<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>BFC的演示</title>
    <style>
        /*第一遍理解记忆：2023-1-17*/
        .box1{
            width:200px;
            height:200px;
            background-color: aqua;
            float:left;
        }
        .box2{
            width:200px;
            height:200px;
            background-color: chartreuse;
            /*开启box2的BFC*/
            overflow: hidden;
        }
        .box3{
            width:100px;
            height:100px;
            background-color: darkorange;
            margin-top:100px;
        }
    </style>
</head>
<body>
    <div class="box1">
        <div class="box3">3</div>
    </div>
    <!-- <div class="box2"></div> -->
</body>
</html>